SANTA BARBARA, Calif. -- Once upon a time, brothers Walt and Roy Disney started a business producing filmed cartoons. For years, the company grew in size and popularity. At one point, the brothers decided to turn an idea into a $17 million amusement park in Orange County, replete with an idealized Main Street and a utopian Tomorrowland.

When the two brothers opened Disneyland on July 17, 1955, 28,000 visitors were greeted by traffic jams, oppressive heat, and dry drinking fountains. It was such an awful experience, the brothers called it Black Sunday.

But today, two generations and 50 years later, a half-billion people have made their pilgrimage to this commercial mecca, transforming a 160-acre development in Anaheim that was once orange groves into an American cultural icon, with clones in Florida, Tokyo, France, and one opening soon in Hong Kong.

''To many people, idealism in America is still expressed by Disney," said William Warner, a professor of English who teaches on media culture at the University of California at Santa Barbara. ''The Main Street, as based on the small town of his early life and [Frontierland], reflecting the pastoral romance of the Old West, are done in an upbeat and optimistic way and engage the American wish to return to something more primal and authentic."

Not surprisingly, Disney officials are more blunt. ''Disneyland has become a national treasure. It's a tradition that's been passed from one generation to the next, almost like the tooth fairy," said Duncan Wardle, a vice president of Disneyland Resorts.

To underscore that point, Walt Disney Co. this month kicked off an 18-month-long celebration of its golden anniversary, drawing crowds not only of children, but nostalgic grown-ups as well. Visitors stood in lines to try the new rides like Buzz Lightyear's Astro Blasters and buy commemorative merchandise such as gold-colored mouse ears. Traditionally, the park sells 80 percent of its mouse ears to children, and 20 percent to adults. But at the kickoff week, adults bought 80 percent of the ears, and depleted the supply, said Wardle.

Depending on whom you talk to, Disneyland is either a safe escape for a conflict-ridden world or an opiate for the unthinking, unimaginative masses.

''Every time I see the Matterhorn [ride], I can't help but think of childhood memories," said Karen Rohde, a suburban mother of two. ''I used to visit Disneyland as a girl, and I still feel its magic."

Charles Wolfe, professor of film studies at UC-Santa Barbara, sees it differently. ''Disney's merchandising culture has constrained and limited the imagination, not only of children, but of the public in general."

Today, Disneyland is one of 11 fantasy theme parks that are part of a $50 billion US conglomerate. It is no longer a small, family-run operation, but a ''sanitized, tightly-wound conglomerate that aims toward perfection," Warner said. It has few of the qualities it boasted 50 years ago and ''is now the antithesis of the homespun idea of America," he added. Alcohol is served at its theme parks, and its films no longer bar profanity, specialists said.

The changes do not seem to matter to millions of consumers. Ask any child if he or she wants to visit Disneyland, and you will hear a familiar refrain. ''I'd rather go to Disneyland than almost anywhere else," said 13-year-old Kevin Rohde of Goleta, Calif. His brother, 9-year-old Dillon, ranks Disneyland alongside its competitor Universal Studios Hollywood.

Indeed, the competition for the eyes and dollars of American children is intense, mother Nina Gustason said. ''Kids have a lot more options, and I think they've become desensitized to the magic of Disneyland."

To fight the competition from Universal and to stay current with rides that offer more thrills than, say, Peter Pan's Flight, Disney Corp. opened the California Adventure Park across the parking lot from Disneyland in February 2001.

That is not the only change: When Disneyland first opened in 1955, admission was $1 -- the equivalent of $7.21 today. Now, admission costs $43 for a child under age 9, and $53 for everyone else -- increasing more than seven times faster than the rate of inflation.

''You have to be a Rockefeller to enjoy Disneyland today," Gustason said. Her family of four spends $212 for admission, $300 for a hotel room, and hundreds more on food and transportation. ''You have to think twice about going there."

Yet the park remains a dreamlike goal for many children. Students at Isla Vista Elementary School in Goleta, about 140 miles from Anaheim, recently raised funds for their school by running in a jogathon. Those who raised $250 would win a free trip to Disneyland.

That inspired three sisters, whose family emigrated from Mexico two years ago, to go door to door after school to raise funds. The sisters -- ages 7, 8, and 9 -- collected hundreds of $1 and $5 pledges. After six weeks, they collected $750 and, last month, joined 38 other students on a bus ride to the Magic Kingdom.

''You should have seen their eyes, so big and shining," said Karen Rohde, who organized the trip. ''More than half of the kids had never been to Disneyland because their families can't afford it."

The rest of the world seems to be adopting the American penchant for nostalgia. When Disney managers ask members of focus groups in Japan or Europe what they like about its parks, they give the same answer, Wardle said. ''It's a magical experience. They go to escape reality and spend time with their loved ones."

Still, Disney's remedy for modern life does not always take root. In 1992, it built a huge park outside Paris, imposing its stylized image of America on Gallic pride. Euro Disney had a glut of hotel rooms and huge building costs, prompting Europeans to deride it as a ''cultural Chernobyl."

It lost money for years.

But the French government recently bailed out Disneyland Paris by offering loan concessions and investments.

Chastened, Disney has recently headed to China, whose middle class of 300 million people is the fastest growing in the world. It is building a Hong Kong theme park that will serve mainland China and reflect the Asian culture. Disney hired a feng shui specialist to help design the park, and every building is blessed with incense once it is completed. In a significant concession to Chinese culture, Disney plans to open the park not on a Friday -- at the start of a weekend -- but on Monday, Sept. 12, a day the Chinese believe is auspicious.

''They've learned from their bad experiences," said Shi Zhang, associate professor of marketing at the University of California at Los Angeles.

At the same time, the company is moving into India, a nation of 1 billion people and about 200 million middle-class consumers. In April, Disney executives Michael Eisner and Robert Iger visited Prime Minister Manmohan Singh, reportedly to lobby his government for land to build a Delhi Disneyland. ''We've become a global enterprise," Wardle said. But to build its worldwide cache, Disney needs to maintain its prestige at home and that is not easy at 50.

And there are questions about Disney's supply of magic, said George Geis, at professor at UCLA's Anderson School of Management. ''Its genius and imagination have been dormant for years. The company has to manage the creative forces skillfully enough to bring back the pixie dust and create something new." Otherwise, the global institution may end up celebrating, over and over, a bygone era that never actually existed.